LMB-2. The phase I clinical trial of recombinant immunotoxin anti-Tac(Fv)-PE38 (LMB-2) was delayed because of a drug shortage but resumed by 2/98 and an additional 11 patients enrolled. The dose limiting toxicity was reached at 63 ?g/Kg QOD X 3 which consisted of reversible ardiomyopathy or transaminase elevations. In this study five partial responses were observed, 3 in HCL, 1 in CTCL and 1 in CLL. Due to the high PR rate in HCL (3/3), a separate study was done testing fresh patient HCL cells ex vivo with LMB-2. Plans were laid to begin clinical testing of LMB-2 for the prevention of GVHD by ex vivo treatment of allogeneic bone marrow, as well as prevention/treatment of GVHD by in vivo administration. In collaboration with Nuclear Medicine, LMB-2 was radiolabeled with In-111 to prepare for imaging/biodistribution studies of LMB-2 in patients being treated for hematologic malignancies. The anti-CD22 recombinant immunotoxin RFB4(dsFv)-PE38 (BL22) was tested for toxicity in mice and monkeys and underwent large-scale production by the MARP for a clinical trial to be done at NIH. The clinical protocol was written and approved with stipulations by the IRB. A study of the ex vivo activity of the immunotoxin toward fresh malignant cells from leukemic patients was completed for publication, and more samples are being tested. HCL cells appear extremely sensitive ex vivo and are being studied separately. A study comparing the liver toxicity of LMB-2 and BL22 was done in hepatocytes and is continuing. RFB4(dsFv)-PE38KDEL was also constructed, purified, and tested on fresh patient cells, in mice and in monkeys. Collaborations were begun with Dr. Gress's group in the Medicine branch to study this agent for purging CLL autografts. Isolation of a new recombinant immunotoxin targeting CD30. Plasmids encoding soluble and membrane forms of CD30 were constructed. Mice were immunized with plasmid encoding full-length CD30. Phage scFv libraries were produced from their spleens, and panned and tested on cellular CD30 and/or recombinant purified sCD30. Several recombinant immunotoxins were produced and characterized, and the isolation of scFv's with higher affinity is continuing. Further work, begun by Vivek Rajagopal, was undertaken on the isolation of PE35, the active translocated fragment of PE38-containing immunotoxins, from the plasma of mice or humans injected with LMB-2. This work is continuing. Work was completed on characterizing new recombinant toxins targeting the urokinase receptor on malignant cells, which use ATF as the ligand. A manuscript is in preparation. Targeting of acute myelogenous leukemia (AML). Art Frankel obtained our plasmid encoding DT388-GM-CSF, and in close collaboration with us, has produced material outside the NIH sufficient for preclinical toxicology studies. To produce new PE38-containing recombinant immunotoxins targeting GM-CSFR, CD33 or CD11b on AML cells, mice have been injected with plasmids encoding these antigens, with the intention of constructing scFv expression libraries suitable for screening on target cells or soluble antigens. The plasmids encoding the soluble forms of these antigens were also constructed to use the recombinant protein for panning or detection of high affinity scFv molecules. With Raffit Hassan, the antibody K1 was developed for imaging in ovarian cancer and mesothelioma. The chemical conjugate K1-PE38QQR was made and tested on target cells. In collaboration with Raj Puri and Robert Rand, the recombinant circularly permuted toxin IL4(38-37)-PE38KDEL was tested as intratumoral therapy in patients with glioblastoma multiforme, and plans are underway, with the help of Neurocrine, to expand the Phase I trial.